A made-up survey asks students two questions and puts the answers in a table.
3 lessons, about 1 h 15 min3 simulations10 problems3 practice questionsPython in every lesson
A two-way table counts people by two answers at once. Once you know one answer, you look at only one row or one column, and the share inside it is a conditional probability, written . This lesson reads conditional probabilities from tables and shows why and are different numbers.
Two answers in a table are independent when the share of one answer is the same in every row or column of the other. Then every count equals row total times column total divided by the grand total. This lesson checks tables for independence and explains why a real sample is never exactly independent.
The expected value of a game is the average gain per play in the long run: each outcome times its probability, added up. A game is fair when its expected gain is zero. A casino game is built with a small negative expected gain for the player, and a simulation shows the average settling exactly there.
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